The military government has called on Thai people to wear yellow because it's connected to the Royal Family.

Rescue mission chief Narongsak Osottanakorn told a news conference the boys were just being children when they got lost and no one was to blame.

"We don't see the children as at fault or as heroes. They are children being children, it was an accident," Narongsak said on Wednesday.

This handout photo made available by the Thai Navy SEAL shows the rescuers holding an evacuated soccer team member during the rescue operations for the youth soccer team. Picture: AP (AP)The boys had to be put into harnesses and high-lined across the rocky caverns during their rescue. Picture: AP (AP)

The Director of Chiang Rai Hospital said the group will need to stay in hospital for seven to 10 days, and will need a further month at home to recover.

"From our assessment, they are in good condition and not stressed. The children were well taken care of in the cave. Most of the boys lost an average of two kilograms," Thongchai Lertwilairattanapong, an inspector for Thailand's health department, said.

One of the American rescuers described the tough conditions rescuers faced. Picture: AP (AP)

Meanwhile one of the Americans involved in the operation described the perilous zero-visibility dives that brought the boys out safely as a "once in a lifetime rescue."

Derek Anderson, a 32-year-old rescue specialist with the US Air Force based in Okinawa, Japan, said that at times during the risky rescue, the boys had to be put into harnesses and high-lined across the rocky caverns. At other times, they endured dives lasting up to half an hour in the pitch-black waters.

"The world just needs to know that what was accomplished was a once in a lifetime rescue," Anderson told The Associated Press.

"We were extremely fortunate that the outcome was the way it was. It's important to realize how complex and how many pieces of this puzzle had to come together."

Boys 'out of danger'

The boys are in reasonably good health, doctors say. Picture: Supplied (Facebook)They will need to stay in hospital for at least the next seven days. Picture: AAP (Facebook)

Thongchai said one from the last group rescued on Tuesday had a lung infection and they were all given vaccinations for rabies and tetanus.

The whole team is recovering well and is out of danger, even though they have lost an average of two kilograms due to spending nine days in the cave without food.

Doctors said that three boys have shown mild symptoms of pneumonia and one is being treated for a cut on his right leg.

Ophthalmologists are checking the boys' eyesight after they spent such a long time in the dark.

The team - called the Wild Boars - have been provided with a soft diet such as rice and chicken, in addition to vitamin supplements.

The first four boys to come out of the cave on Sunday could be given a more diverse dinner on Wednesday.

Thai Prime Minister Prayuth Chan-ocha asked that the boys be given time and space to recover.